CTC-15 restoration

[DaveWM]

Ground stakes on all boards

power resistors on chroma board with crystalized solder pads, reflow

jumper wires on top of chroma board,green corrosion, breaks off. The CRT will turn a solid color like screen control turned up too high.

Grid coupling cap, .01 between the power resistor and a 6GU7 will be weak, the other .01 grid coupling caps for the difference amps will prob be ok.

a trace on the side of the PCB near the horz out tube may fracture, back this up with a buss wire. It connects to a 390k resistor at the horz blanker tube. this shows as a loss of HV due to the blanker tube supplying too much neg bias to the horz out.

Caps in the vert feed back .0082 1kv mainly. the vert out cathode bypass cap, 50uf I think, its on the sweep board. Often ok, but if you doing for someone else then prob should be replaced.

1k power resistor on term strip near vert out trans, ofter the term strip solder has crystalized due to heat.

focus stick, sometimes goes bad mounted to side of fly.

horz output tube coupling cap. I replace this just to be safe.

Filter caps, of course these can be bad, if someone else set then I would restuff the cans just to be safe.

thermistor is fragile often broken.

on off switch is gets a lot of abuse. I use a remote power switch (the kind that are often sold during Christmas time for remote turn on of light) to save wear and tear on all my old vintage stuff.

Check line voltage. PT may have a high line voltage jumper that can be used. Better to use if line voltage is high, which is often the case.

check and adj horz eff coil, often a minor tweak can save 10-15ma or more good for fly life.

Check shunt tube and HV setting per sams. there is a 1k 5% resistor that is used to check voltage drop across for checking current in shunt. Generally you want to see about .5 to 1.5v drop across this while watching normal programing. think you will see this with the HV set to about 23kv and the fly current around 200ma

[6GH8cowboy]

Thanks DaveWM

Good info, esp. the .01 coupling caps in the driver ckt. The .0082 in the vert is rated at 2KV. and is one of the cut components. This seems a bit over kill. I'm thinking 1600v replacement. Thoughts?
There is a thick layer of sticky dust on almost everything. A blower doesn't do much and Deoxit and Q-Tips is an expensive way to cleanup but the results are good. I really need to see everything. Do you have a recommendation?

[DaveWM]

yea 2kv I would stick with that, large pulse from the transformer.

I generally just used compressed air to get the big dust bunnies out of the way, use care around any coils or wires. If it really bothers you I have found rubbing alcohol and q tips works fine.

to check those chroma jumper wires just give them a slight tug, they will break instantly if bad, when they do break they stay put so it looks like they are fine.

there is prob a tube cap on the bottom, connected across the primary of the vert out, think its a .001 2kv and prob one on the audio out as well. May as well replace those, mainly since I cant test them at rated voltage (spikes).

Of course there is the across the line tube cap that should be replaced as well.

What I generally do is scan the parts list for HV caps, and make up an order from that, making sure I have them covered. I get them from mouser, HV caps are found in the film cap section as "snubber" caps.

[6GH8cowboy]

The bright camera flash makes it look better than reality. The cleaned up spots do look better.
I think I'm going to inject a composite video signal and eliminate the tuner and IFs . The display is so bad I can't tell where to begin. I will say that the CRT cathodes are sky high so my dark screen issue will start in the video section. I have re flowed the grounds on the chroma board and that cleared up some filament issues.

[DaveWM]

futz around with the AGC pot. check the control grid voltage on the video out and see if it varies with the brightness setting.

try subbing in a new video out.